The highlighted answer as correct is incorrect. See Bold Text from Per 9.1 B of the vSphere EULA. https://www.vmware.com/download/eula/esx_server.html
(b) Additional License Terms:
VMware grants you a nonexclusive, nontransferable license, without rights to sublicense, to :smileyinfo: install or have installed a single instance of the Software and each Licensed Additional Module on a single Server, unless permitted to have multiple instances on a single Server or to have multiple instances on multiple Servers by the payment of applicable license fees (whether such fees are based on a per Processor, a per Virtual Machine, a per user or any other VMware approved licensing model); (ii) use the Software and each Licensed Additional Module solely for information processing and computing purposes, including the hosting of computer application-based services from a Virtual Machine and provision of such services via an internal or external network, provided such services may not consist of services to a third party that provide primarily computing or processing power (such as utility computing or grid computing) or any computer application-based service that is traded, rented, leased or sold on a Virtual Machine basis; and (iii) use and reproduce the VMware Virtual Infrastructure Client Software or VMware WebAccess (in object code form only) for the purposes of installation and operation on an unlimited number of your own internal computers or terminals solely for the purpose of accessing the Server on which the Software is installed.
Notwithstanding the above, at all times you shall have a valid license for each instance of the Software on any Installed Server regardless of its power state or purpose. For clarification, this includes any and all Servers that may only be temporarily installed with the Software for disaster recovery readiness testing, in the case of an actual disaster or data center migration. Copies of the Software boot media that are made for backup or disaster recovery purposes do not require separate licenses so long as they are not associated with a Server in a way that allows that Server to boot ESX or ESXi from that image; however when such a bootable association is made, said Server constitutes an Installed Server which would require a valid license for the Software.
Blade server license limitation. You may license this software package as part of a license pack or bundle (a "Blade Server License Pack") for installation and operation on a Blade Server. If you acquired the Software as part of a Blade Server License Pack, you may only install and operate the Server Software on a Blade Server and you may not transfer, install or use the Server Software on Servers in a rack-mounted server configuration or on any other Servers. In addition, a Blade Server License Pack must be installed and operated on blades that are plugged into a single chassis.